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## 'Let's Investigate Triangles' printed from http://nrich.maths.org/

Vincent and Tara are making triangles with the class construction set. They have a pile of strips of different lengths.

There are:

**yellow** strips with $3$ holes
**black** strips with $4$ holes,
**red** strips with $5$ holes and
**green** strips with $6$ holes.

There are plenty of strips of each colour.

Vincent makes a triangle with a green strip, a yellow strip and a **red** strip.

Tara makes a triangle with two **green** strips and one **red** strip and another triangle with three **black** strips.

How many different triangles can you make with these lengths?

Can you find three strips which cannot be made into a triangle when you use them together?